MDR stands for "Mateusz' DOS Routines", it is a collection of *.C files (mostly OpenWatcom-targeted) that contain a variety of routines helpful during the development of DOS application.
I am not calling this a "library" because my feeling is that library ought to be strictly organized, have a consistent, uniform API, etc. Here, we really deal with sets of C files.
The general focus of my routines is on 8086-class machines (real mode). My compiler of choice is OpenWatcom.